of wilmington



Patented 22, 1929 DONALD I-IOW'ARD POWEIRS, VTILMINGTQN, DELAWABE,ASSIGNQR T0 I. DU PONT DE NEMOURS 5L7 CGIEPANY, GE WILIvIIN-d-"IQlt,DELAWAE-E, A CGEPORATZUN 0F DELA- WAR-E PROCESS OF VULGANIZIHG RUBBERAND AOCELERATQR THEREFOR No Drawing. Application filcrl June 3,

This invention relates to the vulcanization of rubber and to newaccelerators therefor.

l have discovered that the product resul ing from reaction orcondensation between 2 mols (molecular equivalents) of an aldehyde, 2mols of an amine (particularly a primary amine), and either 1 or 2 molsof carbon disulphide, constitutes an excellent vulcanizationaccelerator. I have also discovered that a similar product or productsmay be obtained by treating an anhydro-aldehydeamine withcarbon-disulphide, or by treating with an aldehyde the substitutedammonium salt of a mono-substituted dithiocarbamic acid. As far as I amaware, the products resulting from the above described reactions havenot heretofore been known.

The combination of equimolecular equiv-alents of aldehyde, primaryamine, and carbon disulphide yields a product having probably thefollowing general formula (I) where R represents hydrogen or ahydrocarbon radical, and R represents an organic radical such as allrylor aryl. For purposes of nomenclature, compounds of this type may beconsidered as lactones of alkyl- (or aryl-)a-mercapto-alkyl-dithiocarbainic acids, such acids having the formula:

These lactone compounds may consequently be designated alkyl (or aryl-)cx-lTlQICElPtO- alkyl-dithio-carbamolactones.

If, instead of combining equimolecular proportions, 2- mols of analdehyde and 2 mols of a primary amine are combined with only one mol ofcarbon disulphide, the resulting 1.925. Serial No. 34,732.

product has probably the following general formula (ll) where R-represents hydrogen or a hydrocarbon radical, and ll represents anorganic radical sucn as alkyl or aryl or derivatives thereof. This sameproduct may be obtained by heating the first product (having Formula I)two mols of such first product apparently condensing, with liberation ofone mol of carbon disulphide.

The products to which the Formula II has been assigned, may be referredto as N-substituted carbothialdines, the term: carbothiah dine havingbeen first used by Delepine, Bulletin de la Societe Chimique de Paris,3d series, vol. 15, page 898, to denote the product obtained bycombining carbon disulphide, acetaldehyde, and ammonia. These newproducts, however, may be more correctly designated: lI-substituted (a)-thion-hexahydrothi-o-(ab,)-diazoles the thio (arbQ-diazole having thegraphical formula tylidene-( Z) -propyl- (ab -di-hydroxyethyl- (a-thion-hexahydrothio- (L5 -diozole, (or, more briefly,cliethylol-butylidene-carbothialdine) having probably the followinggraphical formula:

It is obvious from the above formula that hydrogen sulfide is notliberated in substantial amounts from the reaction.

This compound was tested in the following rubber mixture:

Parts Smoked sheets 50 Amber crepe 50 Zinc oxide 6 Sulphur 6 Accelerator0.75

WVhen cured for 45 minutes at 20 pounds steam pressure, the cured rubberhad a tensile of 2400# at 910% elongation.

II. A mixture of two mols of benzaldehyde and one mol of carbondisulphide is treated with two mole of methylamine at -30 C. The mixtureis then heated to 60 C. for 6 8 hours. On cooling a precipitate of whiteneedles forms. These crystals are filtered off and washed with asolution of sodium bisulphite to remove any excess benzaldehyde. Thematerial is finally washed with water and then dried. This compoundmelted at 130 C. and consisted of practically pure dimethyl-benzylidenecarbothialdine.

This accelerator was tested in the rubber formula given above. Theresulting rubber which had been cured for minutes at J;1: steampressurehad a tensile of 117011: at

v 980% elongation.

III. Two mols of acetaldehyde are added to one mol of carbon disulphideand the mixture cooled in anice bath. Two mols of aniline are addedslowly, with agitation. The mass soon solidifies. It is heated up toabout C. and then allowed to solidify. The

product is nearly pure diphenyl-ethylidonecarbothialdine. lVhen 0.75parts of this compound were incorporated into the rubber compound givenabove and cured for 30 minutes at 40 pounds steam pressure, theresulting rubber had a tensile strength of 2080;;1: at an elongation of870%.

IV. Two mols of n-butyraldehyde and one mol of carbon disulphide aremixed with two mole of butylamine on cn cn crnun Parts Smoked sheets 50Amber crepe 50 Zinc oxide 6 Sulphur 6 Accelerator 0.75

lVhen curved under various conditions of temperature and time, thefollowing results were obtalned.

- Elonga- Tensile Time Temp. tron at strength break Jtfin. D 6' PoundsPercent 3600 775 4240 760 4330 700 Accelerators of the type abovedescribed, especially those made from aliphatic aldehydes and amines,are distinguished by their ability to give good cures at low steampressure (201 without the attendant bad effects of scorching. Moreover,the time of cure may be quite long either at 20.1for 40.72 2 steampressure without producing an overcure. The aging properties of thefinished rubber are excellent.

In addition to the products of the above specific examples, many otheranalogous substances, coming within the generic classes of completelyN-substituted carbothialdines and N-alkyl- (or aryl-)a-mercapto-alkyl-dithiocarbamolact-ones, are valuablevulcanizationaccelerators, among which there may be mentioned:

Dimethyl-ethylidene-carbothialdine,

Dimethyl-n-butylidene-carbothialdine,

Diethyl-elhylidenecarbothialdine,

Diethyl-lnitylidene carbothialdine,

Di-o-tolyl-ethylidene-carbothialdine,

Diphenyl-benzylidene-carbothialdine,

N-methyl-a-mercapto-ethyl-dithio-carbamolactone,

N-methyl-a-mercapto-n-butyl-dithiocarbamolactone,

N-ethyl-a-mercaptoethyl-dithiocarbamolactone,

N-ethyl-a mercaptobutyl-dithiocarbamolactone,

N-o-tolyl-a-mercapto-ethyl-dithiocarbamolactone,

N-phenyl a-IHQTCZLPtOd)G11ZylClltl1lOC&Tl)O inolactone.

(Benzyl and other aryl-methyl radicals are included in the generic term:alkyl.)

Although the process of making the accelcraters and of vulcanizingrubber therewith has been illustrated by reference to specific reagentsand to specific conditions such as proportions, tem'ieratures, etc., itwill, of course, be understood that my invention is not limited to anyspecific substances or conditions of operation.

I claim:

1. The process of treating rubber which comprises combining with therubber a vulcanizing agent and a compound obtainable by chemicalcombination, under conditions preventing substantial liberation ofhydrogen sulfide, of an aldehyde, a primary amine, and carbondisulphide, and vulcanizing the rubber mix.

2. The process of treating rubber which comp 'ises combining with therubber a vulcanizing agent and a compound obtainable by chemicalcombination of 2 mols of an aldehyde and 2 mols or" a primary amine Witha whole number of mols less than 3 of car disulphide, and vulcanizingthe rubber 3. The process of treating rubber which comprises combiningwith the rubber a vulcanixing agent and a compound obtainable bychemical combination of 2 mols of an alde- 'e and 2 mols of a primaryamine with 1 mol of carbon disulphide, and vulcanf the rubber mix.

The process of treating rubber which cmn n-ises combining with therubber a vulcanizing agent and an (a -thion-hexahydrothio-(ebQdiazolehaving as nuclear substituents, groups of the class consisting of alkyland aryl groups, and vulcanizing the rubber mix.

5. it procea the aldehyde and the 'iriinary amine are aliphaticcompounds.

(3. A vulcanized rubber-lilte material de rived from rubber or similarmaterial combined with the product obtainable by chemical combination,under conditions preventsubstantial liberation of hydrogen sulfide, ofan aldehyde and a primary amine with carbon disulphide.

"' A vulcanized rubber derived from rubctined in claim 1 in which ber orsimilar materials combined with sulphur, combined zinc, and the productobtainable by chemical combination, under conditions preventingsubstantial liberation of hydrogen sulfide, of 2 mols of an aldehyde and2 mols of a primary amine with a Whole number or" mols less than 3 ofcarbon disulphide.

8. A vulcanized rubber derived from rubber or similar materials combinedwith sulphur, combined zinc, and the product obtainable by chemicalcombination, under conditions preventing substantial liberation ofhydrogen sulfide, of 2 mols of an aliphatic aldehyde and 2 mols off analiphatic primary amine with a whole number of mols less than 3 ofcarbon disulphide.

9. Vulcanized rubber obtainable by subjecting to a vulcanizationtemperature a rubber mix containing rubber, sulphur, zinc oxide, and anaccelerator comprising the product resulting from reaction, underconditions preventing substantial liberation of hydrogen sulfide,between 2 mols of an aldehyde, 2 mols of a primary amine, and a wholenumber of mols less than 3 of carbon disulphide.

10. Vulcanized rubber obtainable by subecting to a vulcanizationtemperature a ruber mix containing rubber, sulphur, zinc oxide, and anaccelerator comprising the organic product resulting from reaction,under conditions preventing substantial liberation of hydrogen sulfide,between 2 mols of an aliphatic aldehyde, 2 mols of an aliphatic amine,and a whole number of mols less than 3 of carbon disulphide.

l1. Vulcanized rubber obtainable by sub jecting to a vulcanizationtemperature a rubber mix containing rubber, sulphur, and acarbothialdine derivative in which groups of the class consisting ofallryl and aryl groups are substituted for the hydrogen atoms ordinarilyattached directly to the nuclear nitrogen atoms of carbothialdine.

l2. Vulcanized rubber obtainable by sub jecting to a vulcanizationtemperature a rubber i containing rubber, sulphur, and adiallryl-allrylidene-carbothialdine.

l8. Vulcanized rubber obtainable by subjecting to a vulcanizationtemperature a rubber mix containing rubber, sulphur, and from about0.25% to 2% oi a dialkyl-alkylidenecarbothialdine.

14bit rubber-vulcanization comprising a compound obtainable by thechemical combination, under conditions pre venting substantialliberation of hydrogen sulfide, oi an aldehyde, a primary amine, andcarbon disulphide.

15. A rubber-vulcanization accelerator comprising a compound obtainableby the chemical combination, under conditions preventing substantialliberation of hydrogen suliide, 01" an aliphatic aldehyde, an aliphaticprimary amine, and carbon disulphide.

16. A rubber-vulcanization accelerator comprising a compound obtainableby the accelerator chem'ical combination, under conditions preventingsubstantial liberation 01 hydrogen sulfide, of 2 mols of an aldehyde and2 mols of a primary amine with a Whole number of mols less than 3 ofcarbon disulphide.

17. A rubber-vulcanization accelerator comprising a compound obtainableby the chemical combination of 2 mols of an aliphatic aldehyde, 2 molsof an aliphatic primary amine, and 1 mol of carbon disulphide.

18. An alkylidene-carbothialdine of the class consisting of dialkyl anddiaryl alkylidene-carbothialdine, having a strong accelerating action onthe vulcanization of rubher.

In testimony whereof I aiiix my signature.

DONALD H. POWER-S.

